"And if I thought it legalised discrimination, I would have vetoed it."

Presumptive Republican nominee Trump is a protectionist, denouncing the free trade agreement signed by the United States with 11 other countries in the Asia-Pacific region as a threat to American jobs.

Pence, on the other hand, adheres to the laissez-faire economic views that are more conventionally Republican.

Pence has also strongly denounced Trump's proposal last December to close the US borders to Muslims.

He downplayed the disagreement this week when questioned by reporters, saying: "I've taken issue with our candidates from time to time but I'm supporting Donald Trump to be president of the United States of America"